This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Hypothesis: The purpose of this study is to collect data on patients who are on ventilators in the Trauma Surgical Intensive Care Unit (TSICU). We hope this data will help us to determine if one form of assisted breathing is better than another. The two forms of assisted breathing being compared in this study are called BiVent and SIMV. BiVent and SIMV are both delivered by a ventilator but differ in how they assist breathing. SIMV is an older form of mechanical breathing that blows air into the lungs to inflate the lungs. BiVent is a newer form of mechanical ventilation that permits the patient to pull air into the lungs as we normally do. Both BiVent and SIMV are currently being used on a regular basis in the TSICU. It is our hope that this study will determine if one method of assisted breathing is better than another in preventing complications associated with mechanically assisted breathing.